1. Technical Field
The present invention relates to sensor elements, methods for manufacturing a sensor element, sensor devices and electronic apparatuses.
2. Related Art
Angular velocity sensors (vibration gyro sensors) have been known (see, for example, JP-A-2008-14887 (Patent Document 1)) as sensor elements that are used for body control in vehicles, self-position detection of car navigation systems, vibration control and compensation systems (such as, shake compensation) for digital cameras, digital video cameras, and the like, and detect physical quantity, such as, angular velocity, acceleration and the like. For example, an angular velocity sensor described in Patent Document 1 has a tuning-fork element formed from two arms and a connection section that connects one ends of these two arms. Also, in the angular velocity sensor described in Patent Document 1, the tuning-fork element is formed from non-piezoelectric material, and each of the arms is provided with a driving section made of a pair of electrodes and a piezoelectric thin film sandwiched therebetween and a detecting section.
In the angular velocity sensor described in Patent Document 1, a voltage is applied between the pair of electrodes of the driving section, thereby flexurally vibrating (driving) the arms. In this driving state, when the arms receive an angular velocity about their axis extending along the arm's longitudinal direction, the arms bend in a direction orthogonal to the driving direction due to Coriolis force, and a charge according to the amount of the bend is detected by the pair of electrodes. The angular velocity can be detected based on the detected charge.
The tuning-fork element having the two arms described above may generally be formed by etching a substrate. However, it is difficult to obtain accurate dimensions of the tuning-fork element according to the design due to etching anisotropy of the substrate, variations in working process, and the like. As a result, the tuning-fork may be formed into a shape that is not originally intended, such that the arms may bend in a direction that is different from the driving direction, even when the arms are not subjected to an angular velocity. If a charge that is generated by the pair of electrodes at the detecting section, which may be caused by such bending of the arms, is detected, the detection accuracy would be deteriorated.
Therefore, according to the angular velocity sensor described in Patent Document 1, a portion of one of the pair of electrodes at the detecting section 1 is removed, thereby adjusting the amount of charge to be outputted from the pair of electrodes at the detection section in the state where no angular velocity is applied to the arms. However, according to the angular velocity sensor described in Patent Document 1, it is difficult to make highly accurate adjustment of the amount of charge to be outputted from the pair of electrodes at the detection section.